/**
   * Closes the cache and deletes all of its stored values. This will delete all files in the cache
   * directory including files that weren't created by the cache.
   */
  @Throws(IOException::class)
  fun delete() {
    cache.delete()
  }

  /**
   * Deletes all values stored in the cache. In-flight writes to the cache will complete normally,
   * but the corresponding responses will not be stored.
   */

// dataUsageCacheV2 contains a cache of data usage entries version 2.
type dataUsageCacheV2 struct {
	Info  dataUsageCacheInfo
	Cache map[string]dataUsageEntryV2
}

// dataUsageCacheV3 contains a cache of data usage entries version 3.
type dataUsageCacheV3 struct {
	Info  dataUsageCacheInfo
	Cache map[string]dataUsageEntryV3
}

// dataUsageCacheV4 contains a cache of data usage entries version 4.

  calls.push_back(block_size);
  // Cache miss followed by cache hit.
  TF_EXPECT_OK(ReadCache(&cache, "", block_size, 1, &out));
  TF_EXPECT_OK(ReadCache(&cache, "", block_size, 1, &out));
  calls.push_back(2 * block_size);
  // Cache miss followed by cache hit.  Causes eviction of LRU element.
  TF_EXPECT_OK(ReadCache(&cache, "", 2 * block_size, 1, &out));

    getAll(cache, asList(6, 8));
    CacheTesting.drainRecencyQueues(cache);
    ticker.advance(1, MILLISECONDS);
    assertThat(keySet).containsExactly(1, 3, 6, 8);

    // get fails to save 1, put saves 3
    cache.asMap().put(3, -3);
    getAll(cache, asList(1));
    CacheTesting.drainRecencyQueues(cache);
    ticker.advance(1, MILLISECONDS);
    assertThat(keySet).containsExactly(6, 8, 3);

    return Math.max(accessQueueSize(cache), writeQueueSize(cache));
  }

  static void processPendingNotifications(Cache<?, ?> cache) {
    if (hasLocalCache(cache)) {
      LocalCache<?, ?> cchm = toLocalCache(cache);
      cchm.processPendingNotifications();
    }
  }

  interface Receiver<T> {
    void accept(@Nullable T object);
  }

  /**

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    for (LoadingCache<Object, Object> cache : caches()) {
      checkEmpty(cache);
    }
  }


  public void testInvalidate_empty() {
    for (LoadingCache<Object, Object> cache : caches()) {
      cache.getUnchecked("a");
      cache.getUnchecked("b");
      cache.invalidate("a");
      cache.invalidate("b");
      cache.invalidate(0);
      checkEmpty(cache);
    }
  }

    getAll(cache, asList(6, 8));
    CacheTesting.drainRecencyQueues(cache);
    ticker.advance(1, MILLISECONDS);
    assertThat(keySet).containsExactly(1, 3, 6, 8);

    // get fails to save 1, put saves 3
    cache.asMap().put(3, -3);
    getAll(cache, asList(1));
    CacheTesting.drainRecencyQueues(cache);
    ticker.advance(1, MILLISECONDS);
    assertThat(keySet).containsExactly(6, 8, 3);

 * by the garbage collector. Entries with reclaimed keys or values may be removed from the cache on
 * each cache modification, on occasional cache accesses, or on calls to {@link Cache#cleanUp}; such
 * entries may be counted in {@link Cache#size}, but will never be visible to read or write
 * operations.
 *

        assertTrue(cache.asMap().remove(key, value));
        assertFalse(cache.asMap().remove(key, -1));
        assertFalse(cache.asMap().containsKey(key));
      }
      checkEmpty(cache);
    }
  }


  public void testKeySet_populated() {
    for (LoadingCache<Object, Object> cache : caches()) {
      Set<Object> keys = cache.asMap().keySet();